Mavic GP4, any good?

Hey,
about to rebuild up this track bike I have, and wanted to do it with tubulars. Found a pair of Mavic gp4s for pretty cheap. Are they any good? I googled 'em, but cannot seem to find what I am looking for. Usually I roll on Velocity Deep Vs, or Richey Aero rims (both clincher). Any thoughts? Are they gonna hold up if I roll around on the street? I know the old tubular on the street story, but I think it will be cool. Lastly, are they fairly easy to build up? Velocities are pretty simple, and stay true.